Five parts. Each one feeds the next, and each one can quietly break the others.
Picture the business as a pipe with five joints. Money goes in at one end as ad spend. Profit comes out the other as repeat orders. Every joint leaks.
| Part | The question it answers | The number that tells you | Where it leaks |
|---|---|---|---|
| 1. The numbers | What does one order leave after every cost? | Contribution margin per order | Returns, shipping and discounts nobody priced |
| 2. The stranger | What does a new customer cost, really? | New-customer acquisition cost, blended | Paying for buyers who would have come anyway |
| 3. The offer | Why this, why now, why you? | First-order conversion and second-order rate by offer | Offers that win bargain hunters |
| 4. The owned channels | Do they come back without another ad? | Second-order rate and revenue per subscriber | Missing flows, a shrinking list, the spam folder |
| 5. The proof | Which of this is working? | Cohort contribution at 90 and 180 days | Reports built on calendar months and platform claims |
The joints interact, and that’s the reason to learn all five. A deeper discount lifts part 2 and quietly lowers parts 1 and 4. A stronger welcome series makes paid acquisition look better, because the platform takes credit for orders the email closed. A deliverability problem shows up as “campaigns stopped working” and gets fixed with more campaigns, which makes it worse.
Most teams are organized by channel: a paid person, an email person, a site person. Each optimizes their joint. Nobody owns the pipe. This book is written for whoever should.
This is one chapter of The Whole Machine, which is free and readable in full on a single page with no form in front of it.